Burns are common diseases in peacetime and wartime, especially in wartime. After burn, the mortality rate, appearance damage rate and mutilation rate are high, the treatment period is long, which directly threaten the life safety and the health of the body, which brings heavy burden to the society and the family.
At present, the accurate judgment of the degree of skin tissue damage caused by burns is still a major problem in burn surgery, but the most common method used in clinical diagnosis of burn depth still mainly relies on clinical experience, including the observation of the appearance of the burn wound, the condition of capillary refill, and the feeling of the wound on the touch and the pain of acupuncture, etc. Data shows that accuracy of the empirical diagnosis of wound surface by the world's best burn doctors is only about 70%, that is, at least 30% of the healthy tissue may be incorrectly cut or 30% of the necrotic tissue may be retained undesirably during the burn operation. The former can remove extremely valuable skin appendages and its related stem cells remaining on the wound and other normal tissues along with necrotic tissue, and this has an important influence on the speed and quality of wound healing. The latter can increase the depth of the burn, that is, wound may become deeper. In addition, deep burn skin tissue lesions can be deep into the muscle and even bone, which is far beyond the anatomical depth of the skin tissue, and the treatment and prognosis of this kind of injury are more complicated, therefore, the empirical diagnosis of burn depth only based on the naked eye identification has a limited guiding effect for the clinical treatment. Research data show that timely and accurate judgment and treatment can inhibit the speed and extent of the change of the burn wound surface from the superficial to the deep, and can effectively save the lives of patients, reduce complications, promote wound healing, accelerate the rehabilitation of patients.
The current “golden standard” for the burn diagnosis is still tissue pathological biopsy. There are several reasons why this cannot be applied to clinical practice: 1. the operation of a biopsy is traumatic to the body, which is not acceptable to some patients; 2. in a certain period of time, the pathological changes of the burned tissue are dynamic and continuous, therefore, it may not accurately predict the results by performing a single biopsy so as to preliminarily assess the damage degree in the early stage of the burn; 3. an experienced pathology expert is required, and this expert has to commit to this work for a long time. For the same reasons, skin collagen and immunohistochemical staining of vimentin technology that appeared subsequently also failed to be popularized in clinical testing.
Since the sixties of the 20th century, a variety of diagnostic techniques of burn depth have emerged in the field of burn wound diagnosis, such as fluorescence detection technique, near infrared thermal imaging technique, ultrasonic detection technique, laser Doppler technology, spectral Biotechnology and so on.
Fluorescence detection technique uses intravenous injection of fluorescent substance to evaluate the depth of the wound according to the fluorescence intensity, peak value and time phase characteristics, which are produced when the wound is irradiated with different excitation light. However, substances such as the wound ointment, antiseptics, dressing, and biological agents have a relatively great impact on the ICG detection results of the burn wound. In addition, the fluorescence is weak when the deep burn blood vessel is damaged or is blocked, which increase detection error.
Infrared thermal imaging technique evaluates burn depth of the wound by detecting the thermal radiation of different burn skin. Lawson et al. firstly use this technique to detect the depth of the wound. However, this method has higher requirements for the detection condition, and needs constant ambient temperature and equilibrium time, both evaporation and cooling of wounds greatly affect the detection results. Due to high equipment cost, large individual difference, high false positive and many other factors, Deep II and III degree wounds cannot be well distinguished, limiting its wide application in clinical.
Kalus evaluated burn depth by first using B ultrasound scan, the main principle of which is to observe the boundary of living tissue and necrotic tissue, and then diagnoses based on the echo patterns of normal skin and different burn tissues. The main factor that limits its clinical application is that contact of the wound during the operation is required. In addition, practice has proved that the diagnostic accuracy is low, and is not superior to the subjective empirical diagnosis.
Laser Doppler technique products are currently the only device approved by the United States FDA to be used for the diagnosis of burn wound depth. Its principle is to use the Doppler shift to detect blood cell flow in the micro blood vessels of the wound tissues. The blood flow of superficial burn wound is relatively rapid, and that of the deep burn wounds is slow, so the superficial and deep burns can be distinguished based on this.
Early spectral technique evaluates the depth of burn using different attenuation of different spectra after absorption by blood in the wound. Anselmo et al. first proposed this technique and used it in clinical diagnosis. Three kinds of spectra green, red and blue were used to diagnose the wound, and the accuracy rate of diagnosis is as high as 79%. Based on this technique, an instrument designed by Heimbach et. al. used in clinic has 80% diagnostic accuracy of the wound that was not healed in three weeks. In recent years, the method based on spectral technique to diagnose burn depth has been further developed and gradually extended to the field of near infrared spectroscopy. In 2001, Sowa et al. developed a new method to judge the depth of burn using differences of oxygenated hemoglobin, deoxygenated hemoglobin and tissue moisture in the blood when the skin is burned shown in the absorption spectra of near infrared light in a wavelength range of 700-1000 nm, and measuring the total hemoglobin in the blood (tHb), tissue oxygen saturation (StO2) and water (H2O) content, and carried out the experimental study on the animal model of 3 h after injury. In 2005, Milner et al. evaluated the degree of burn by orthogonal polarization spectral (OPS) of wavelength 548 nm (hemoglobin absorption wavelength) for the first time. In 2009, Cross et al. studied the relationship between the degree of edema of skin tissue and the burn depth after burn in the wavelength range of 500-1000 nm. However, the core principles of the above research are to judge the depth of burn indirectly based on the changes of oxygen carrying status of red blood cell in blood, and tissue water content changes of the skin before and after skin burn (see FIG. 9), and precise information about the depth and area of burn skin tissue necrosis cannot be provided directly.
At present, spectral imaging technique has matured, and is used in the field of space remote sensing and mapping, agriculture, exploration and other fields of science and technology. This technique combines spectral analysis technology with image analysis technology, and meets the new concept of comprehensive qualitative, quantitative and positioning analysis, its visualization, non-contact and non-invasive and other excellent characteristics show its potential probability to be used as a new kind of high specificity and high accuracy burn wound diagnosis tool. At present, its imaging band is mainly in the visible and near infrared spectrum, but the spectral resolution is generally low, and the scanning precision is about 50 nm, which cannot meet the needs of medical fine research yet. Currently, the bands of imaging spectrometer for the study of burn medicine are mainly in 400-700 nm and 700-1100 nm, the basic principle of the spectral biology is still mainly analyzing the changes of oxygen carrying status of red blood cells in the blood and tissue water content of the skin. Among them, a typical patent literature is “visible-near infrared spectroscopy technology in burn injury assessment” (U.S. Pat. No. 860,554 B2), which mainly studied changes of oxygenated hemoglobin, deoxyhemoglobin, and water content of the blood of the skin before and after burn in 500-1100 nm band, and the depth of burn is indirectly suggested; therefore, accurate information about skin tissue necrosis cannot be provided.
The existing spectral imaging techniques can not accurately distinguish the skin necrosis tissue and acquire the spectral images of the skin tissue tomography, there is also a key point that the spectral resolution and imaging spectral range thereof cannot distinguish skin necrotic tissue and acquire the tomography images thereof, that is, a high resolution narrow band and wide band tunable filter is the core problem.
Therefore, so far, there is no such diagnostic equipment and related methods which can directly and accurately distinguish the depth of the necrotic tissue, accurately identify the boundaries of the necrotic tissue and normal tissue.